The present invention relates to a record and playback device, such as a digital VCR, for recording or playing back data including a video signal and an audio signal.
Recently an innovative broadcasting method is developed such as a high definition television (HDTV), and in the U.S., a digital television (DTV) method has been commercialized.
In the DTV broadcasting system, a video signal is coded through Moving Picture Experts Groupxe2x80x942 (MPEG 2) method and is combined with a multi-channel audio signal, e.g. by a Dolby Digital method, then is broadcast as a digital broadcasting. Meanwhile, MPEG 2 is disclosed as 13818 standard of International Organization for Standardization/International Electro-technical Commission (ISO/IEC). The digital broadcasting features that multi-channels can be transmitted with quality picture in a narrow frequency bandwidth because video signals are compressed and coded.
In this climate, portable devices and studio devices capable of the HDTV method have been developed. However, those devices are expensive and thus producing the program for the HDTV broadcasting incurs a lot of cost and time. Accordingly the program is sometimes produced by converting a cinema film to TV application. In the U.S., film oriented programs are usually on-aired through the DTV.
Cinema-film has typically has 24 frames per second, i.e. it produces a progressive scanning signal of 24 Hz frame frequency (hereinafter referred to as a 24p signal). On the other hand, a VCR handles a TV signal of 30 Hz frame frequency. Therefore, conversion of the frame frequency is necessary. Converting a cinema film into TV signals is generally called telecine conversion. This conversion is known as 2:3pull down technique.
When the converted signal through 2:3pull down technique is recorded in a conventional VCR, the same field is repeated, which limits an edit process. Therefore, it is desired that the cinema film as it is, i.e. at a frame frequency of 24 Hz, to be recorded with the VCR.
In audio devices, DVD-AUDIO standard is established for digital Versatile Disc (DVD). According to this standard, an audio signal sampled at 96 kHz is recorded and played back, and sound of the higher quality than that of a conventional method is obtainable. As such, due to an introduction of a digital technique, an audio signal of higher quality is going to be available at home.
An instance of the VCR that records and plays back the HDTV signal is HD-D5xc2x7VCR. A video signal is coded complying with HD-D5 method which is disclosed in 342M standard of Society of Motion Picture and Television Engineers (SMPTE). The HD-D5xc2x7VCR is disclosed in SMPTE 279M standard.
The HD-D5xc2x7VCR records and plays back a video signal of interlace scanning and an audio signal of four channels. Details of respective signals are as follows:
video signal; a number of scanning lines=1125 lines, a number of active scanning lines=1080 lines, field frequency=60 Hz (or 59.94 Hz)
audio signal; sampling frequency=48 kHz, a number of quantizing bits=20.
When a video signal of 24 Hz frame frequency is recorded with the VCR discussed above, an equivalent frequency for overall signal process is lowered by 24 /30 for record and playback comparing with the case where a video signal of 30 Hz frame frequency (60 Hz field frequency) is recorded.
Data amount per frame of the video signal remains the same regardless of 24 Hz or 30 Hz frame frequency, therefore, changing the rotational components from 24 Hz system to 30 Hz system allows video data to be recorded in the same tape format.
On the other hand, as for the audio signal, input data corresponding to one field of the video signal are collected in every input channel, and an error correcting code is added before the audio signal is recorded.
In the case of recording a video signal of 30 Hz frame frequency, a number of audio samples per one channel, one field of a digital audio signal sampled at 48 kHz is 48000/60=800. In the case of 24 Hz frame frequency, it is 48000/48=1000. As such, the numbers of samples per field are different between 24 Hz and 30 Hz, the audio signal thus cannot be recorded in the same recording area.
Then an audio sampling frequency is converted to 48000xc3x9724/30=38400 Hz by using a digital filter. A number of samples of the audio signal of which sample frequency is converted to 38.4 kHz is 38400/48=800 per one channel and one field, this is the same value as the case where a frame frequency is 30 Hz. Thus this audio signal can be recorded in the same recording area on tape.
However, the method discussed above uses the digital filter for converting the audio sampling frequency, and this deteriorates sound quality depending on a number of taps or bits. Further, this lowers the sampling frequency, and if the original frequency bandwidth is not limited to a certain extent, return distortion would occur. Therefore, the frequency bandwidth of the input audio signal should be limited.
The conventional method discussed above records and plays back only an audio signal of four channels. When a program material for the HDTV is made from a cinema film, an original cinema film contains audio signals in multi-channel form typically represented by Dolby Digital method. The Dolby Digital method uses the data of six channels while a VCR which records and plays back the cinema film only uses four channels for audio signals. For recording the audio signal of the cinema film as they are, the VCR which can uses at least six channels or preferably eight channels is demanded.
The conventional method discussed above records and plays back only the audio signal sampled at 48 kHz, and cannot record and play back a higher quality sound such as the audio signal sampled at 96 kHz or the audio signal quantized with 24 bits.
In general, two methods are available to increase a number of audio channels.
The first method is to compress the audio data more than four channels to the data of four channels, and record the compressed data with the conventional VCR. However, when the data is compressed, sound quality is somewhat lowered, therefore, this method cannot be accepted as a VCR for producing a source program. Further, the compression produces some delay, and this causes the entire system to be complicated. The compression further amplifies the influence due to an error produced in the VCR.
The second method is to develop a totally new tape format complying with the multi-channel audio signals. Developing the new tape format allows arbitrary design of devices; however, it takes a lot of time and costs a lot of money for developing the devices, and it is difficult for a new device to be compatible with the conventional format.
For usability of the VCR, it is desirable that a conventional record/playback devicexe2x80x94which handles audio data of only four channelsxe2x80x94plays back a recorded medium, in which audio data of more than four channels are recorded, to reproduce the sound of four channels (downward compatibility). It is also desirable that a recorded mediumxe2x80x94which was recorded with the conventional record/playback devicexe2x80x94is played back with a record/playback device, capable of handling more than four channels, to reproduce sound of four channels (upward compatibility).
The present invention addresses the problems discussed above.
A record/playback device of the present invention complies with a first format in which a first video signal and a first audio signal are to be recorded, and a second format in which a second video signal and a second audio signal are to be recorded. The second video signal has a lower frame frequency than the first video signal and the second audio signal has the same data amount per unit time as the first audio signal. The record/playback device comprises the following elements:
(a) a video processor for outputting video recorded data having the same frame frequency as an input video signal, where the input video signal is the first or the second video signal;
(b) an audio processor for providing an input audio signal with shuffling and adding of an outer code, then outputting audio recorded data per frame or field of an input video signal. The input audio signal is the first or second audio signal; and
(c) a recording processor for digitally recording the output data from the video processor and the audio processor onto a recording medium.
The audio processor equalizes coding amount of audio recorded data of the first format with that of the second format per field or frame. The record/playback device records, both in the first format and the second format, the video recorded data and audio recorded data in the same recording-track-format onto a recording medium.
The record/playback device of the present invention complies with a first, second and third formats. The details of respective formats are as follows: (1) The first format records the first video signal and the first audio signal. The first audio signal is quantized with n (n=a natural number) bits. (2) The second format records the first video signal and the second audio signal. The second audio signal is quantized with m (m=a natural number and m greater than n) bits. (3) The third format records the second video signal having a lower frame frequency than the first one, and a third audio signal.
The record/playback device comprises the following elements in order to comply with the second and third formats in addition to the first format:
(a) a video processor for outputting video recorded data having the same frame frequency as an input video signal, where the input video signal is the first or the second video signal, and where the video processor outputs the second video signal as video recorded data in the third format;
(b) a first audio processor for outputting a first audio recorded data in the first format, where the upper xe2x80x9cnxe2x80x9d bits data of the second audio signal has undergone a shuffling process and an adding process of an outer code.
(c) a second audio processor for outputting a second audio recorded data in the second format, where the lower (mxe2x88x92n) bits data of the second audio signal has undergone the shuffling process and the adding process of an outer code;
(d) a third audio processor for outputting a third audio recorded data in the third format, where the third audio signal has undergone the shuffling process and the adding process of an outer code;
(e) a multiplexer for multiplexing the first audio recorded data and the second audio recorded data; and
(f) a recording processor for recording the video recorded data and the audio recorded data onto a recording medium, where the audio recorded data is an output from the multiplexer or the third audio recorded data.
The first audio recorded data, the outer code amount of the second audio recorded data and the outer code amount of the third audio recorded data have the same data quantity.
The record/playback device of the present invention complies with the first format which records a video signal and the first audio signal as well as the second format which records the video signal, the first and second audio signals. The device comprises the following elements in order to complies with the first and second formats:
(a) a video processor for outputting the video signal as video recorded data in the first format;
(b) a first audio processor for outputting the first audio signal as first audio recorded data in the first format;
(c) a second audio processor for outputting the second audio signal as second audio recorded data in the second format;
(d) a multiplexer for multiplexing and outputting the video recorded data, first audio recorded data, and second audio recorded data;
(e) a recording processor for recording the multiplexed data digitally onto a recording medium.
In the case of the second format, the recording processor works at higher than N2 times processing speed when it records in the first format (N2 is a bit-rate ratio of the second format vs. the first format). The recording processor records the second audio signal into an area corresponding to the area of the recording medium where the first audio signal is recorded.
Further, the record/playback device of the present invention complies with the first format recording the video signal and the first audio signal as well as a third format recording the video signal and the third audio signal. The device comprises the following elements in order to comply with these two formats:
(a) a video processor for processing a video signal and outputting video recorded data in the first format;
(b) a converter for converting the third audio signal into a-fourth audio signal which is in the same specification as the first audio signal and a fifth audio signal in accordance with a given rule in every time sequence;
(c) a first audio signal processor for processing the fourth audio signal and outputting the first audio recorded data in the first format;
(d) a second audio processor for processing the fifth audio signal and outputting the second audio recorded data in the second format;
(e) a multiplexer for multiplexing the video recorded data, the first and second audio recorded data, and outputs the multiplex recorded data; and
(f) a recording processor for recording the multiplex recorded data digitally onto a recording medium.
The recording processor works at the processing speed higher than N times of recording in the first format (N is a bit-rate ratio of the second format vs. the first format). The recording processor records the second audio signal in an area adjacent to the area of the recording medium where the first audio signal is recorded.